1. Field of the Invention
The invention relates to a method for manufacturing a pixel structure, and in particular, to a method for manufacturing a pixel structure, which utilizes a lift-off process to manufacture a passivation layer.
2. Description of Related Art
Displays are a communication interface between human and information. Currently, flat panel displays are the main trend in development. The flat panel displays may mainly have the following categories: organic electroluminescence display, plasma display, and thin film transistor liquid crystal display (TFT-LCD), in which TFT-LCD is the most widely used. In general, a TFT-LCD is constituted by a TFT array substrate, a color filter array substrate, and a liquid crystal layer. The TFT array substrate includes a plurality of scan lines, a plurality of data lines, and a plurality of pixel structures arranged in an array. Each pixel structure is electrically connected to the corresponding scan line and data line.
FIGS. 1A to 1G are schematic views of a conventional method for fabricating a pixel structure. Referring to FIG. 1A, first, a substrate 10 is provided, and a gate 20 is formed on the substrate 10 using a first photolithography and etching process. Next, referring to FIG. 1B, a gate insulating layer 30 is formed on the substrate 10 to cover the gate 20. Afterwards, referring to FIG. 1C, a channel layer 40 above the gate 20 is formed on the gate insulating layer 30 using a second photolithography and etching process. In general, a material of the channel layer 40 is amorphous silicon. Then, referring to FIG. 1D, a source electrode 50 and a drain electrode 60 are formed on partial regions of the channel layer 40 and the gate insulating layer 30 using a third photolithography and etching process. Observed from FIG. 1D, the source electrode 50 and the drain electrode 60 respectively extend onto the gate insulating layer 30 from both sides of the channel layer 40, and expose a portion of the channel layer 40. Next, referring to FIG. 1E, a passivation layer 70 is formed on the substrate 10 to cover the gate insulating layer 30, the channel layer 40, the source electrode 50, and the drain electrode 60. Thereafter, referring to FIG. 1F, the passivation layer 70 is patterned by a fourth photolithography and etching process to form a contact hole H in the passivation layer 70. In FIG. 1F, the contact hole H in the passivation layer 70 exposes a portion of the drain electrode 60. Then, referring to FIG. 1G, a pixel electrode 80 is formed on the passivation layer 70 by a fifth photolithography and etching process, and observed from FIG. 1G, the pixel electrode 80 is electrically connected to the drain electrode 60 through the contact hole H. After the pixel electrode 80 is formed, the fabrication of the pixel structure 90 is completed.
In view of the above, the conventional pixel structure 90 is mainly fabricated by the five photolithography and etching processes. In other words, the pixel structure 90 must be fabricated with the five photo-masks of the different patterns. The photo-masks are of high price, and each photolithography and etching process requires a photo-mask of a different pattern. If the photolithography and etching processes cannot be simplified, the fabrication cost of the conventional pixel structure cannot be reduced.
Besides, with the increasing of the size of the TFT-LCD panel, the size of the photo-mask for fabricating the TFT array substrate is also enlarged, so the photo-mask of a larger size becomes more expensive, and the fabrication cost of the conventional pixel structure cannot be effectively lowered.